Geometrical navigation instrument



Aug. 3, 1948. J. P. PU-TNAM 2,446,433

GEO METRICAL NAVIGATION INSTRUMENT Filed Dec. 8, 1944 2 Sheets-Sheet 1 Ag- 1948. J. P. PUTNAM 3 GEOMETRI CAL NAVIGATION INSTRUMENT Filed Dec. 8,1944 2 Sheets-Sheet lNvaN-Fu R:

Patented Aug. 3, 1948 .GEOMETRICAL NAVIGATION INSTRUMENT .101111 P:Putnam,- Boston, Mass.,- assignor to- The 1 TReece" Corporation, acorporation of Maine Application December 8, 1944, SerialNo. 567,138

3 Claims. (01. 33-1) 1 2 This invention relates to navigation instru-Fig. lis a diagram illustrating the principle of ments and moreparticularly'though not excluoperation involved in the presentinstrument. sively, to instruments for use in aerial naviga- Fig, 2 is afragmentary top plan view of the tion. instrument.

The instrument to which the present inven- Fig. 3 is a sectionthroughthe instrument taken tion pertains is of the type'disclosed in my priorsubstantially along the line '3--3 of Fig. 2. Patent No. 2,357,131,dated August 29,1944. This Fig. 4 is a fragmentary section taken on theinstrument can be set in accordance with such line 4-4 ofFig. 2. readilyascertainable data as the true course of V Fig. 5 illustrates a detailof the instrument. an objective to be reached, the compass variav Fig.6is aperspective view of the active parts tion of th locality,the-indicated airspeed of a of the instrument'shown disassembled. plane,the air temperature, the. altitude at which ,"Briefly, the principle onwhich the present the plane flies, and thejdirection and velocity ofinstrument is based involves the following. A the wind, whereupon theinstrument-will-immelinear, uniformly graduated speed scale I! (Fig.diately and directly indicate the groundspeed of 1) carries at the zeropoint thereof a transverse the plane and the magnetic course to befollowed pivot or stud l8, and slidably receives a floating in order toreach the objective under these con- .pivot or stud l9. Each of thepivots i8 and I9 ditions. The instrument includes a plurality of isindependently movable radially of, and circuseparately coaxiallyturnable discs which arerellarlyabout, a fixed common axis at. In usingatively angularly adjusted f;or' the purpose of 0 the instrument thepivot I8, is, in anydisposisetting the instrument-in. accordance-withthe tion of the scale ll, adjusted radially of the dat above m ntio s wel s o her operatin fixed axis a: such that the lengthof the radial partsof which one is. a; linear scale on-which arrow orvector a represents,in the calibration the ground speed is read. for anysetting ofthe of thespeed scale [1, the indicated air speed of instrument. The. variousdiscsand other operavplane. The floating pivot I9 is thereupon adating partsof the instrument are superposed upon justed radially of,and/orcircularly about,thefixed one another such that the majorityv of, themaxis a: such that the radial arrow or vectorbpoints overlie the groundspeed scale and,;being made in the direction of the. prevailing Wind andits of transparent material, render the ground-speed lengthrepresents,xalso in the calibration of the scale visible from the top ofthe instrument. speed scale'll, the wind velocity. The scale I? However,lack of complete transparency of the may then assume the full lineposition shown in discs themselves, together with the cumulative Fig. 1,forinstance, and point in the true diglare resulting from lightreflection from-the rection of flight of the plane as well as indicatesurfaces of the discs and operating parts overthe ground speed of thesame opposite the pivot lying the ground speed scale, whose graduations"I9, if theplane is headedjin the direction of the are necessarilyrelatively closely spaced somevector a. However, the track or truecourse whatobscures thelatter and renders the readto the objective to bereached is represented by ing of the ground speed thereon difficult. thearrow 2, wherefore the track or true direc- It is the primary aimand'object 'of'the prestion of flight of the plane has to coincide withent invention to arrange'the discs and other pp- 40 said arrow. This isaccomplishedby merely erating parts of the instrument so that none ofcircularly adjusting the pivot I8 about the fixed them ever coversthatportion of the groundspeed axis a: until the scale ll assumes thedot-andscale on which'theground speed is to be read dash line positionllfl parallel to the true course for any setting of the instrument. 2.Such circular adjustment ofithe pivot l8 The foregoing and other.objectsof'the inven- 5 changes neither the length of the vector a(reption, together with means Whereby'thelatter may be carriedintoefie'ct: will best beunderstood' from the following description ofan'illustrative embodiment shown in the, accompanying} drawings: inwhich,

resenting the indicated airspeed of the plane), nor'the length orangular disposition of the. vector b (representingfthe direction andvelocity of the wind), with the result that the. ground speed oftheplane is indicated on the dot-and-dash line scale ll opposite the pivotl9 when the plane is headed in the direction of the vector u, but fliesactually in the direction of the track 2 due to side drift caused by thewind. If there is no wind, the pivot i9 is radially shifted intocoextension with the common axis a so that the wind vector becomes zero.

Referring now particularly to Figs. 3 and 4, the instrument embodyingthe principle just de scribed comprises a base plate 2% above which aredisposed, in parallel, superposed, coaxial relation, and in the ordernamed, a wind velocity disc 2i (see also Fig. 6), a wind direction disc22, a track link 23 carrying the above-mentioned ground speed scale H, afour-bar linkage 2d, a track pointer 2'5, a heading disc 26, an airspeed disc 21, an air speed correction disc 28, a magnetic compass disc29, and a top or truecompass point plate or disc 30. All of the abovenamed parts, with the possible exception of the base plate 20, arecomposed of transparent (preferably sheet plastic) material to rendervisible,

through overlying parts, scale graduations and other inscriptions (to bedescribed) on underlying parts.

The various operative elements are maintained in cooperating operativeinterrelation by support members including the base plate 28 as follows:the top disc 38 is received with its periphery in arcuate recesses 35 inthe .top of two opposite spacers 36 (Figs. 2 and 4), and is firmly heldtherein against rotation by retainer plates 37. A plurality of screws 38secure the retainer plates 31 to their respective spacers 3B and thelatter to the base plate 28. The lowermost wind velocity disc 2| isjournalled coaxially of the to? disc 30 on a stud 40 which projects fromthe base plate 20, while the remaining discs 22, 26, 21, 28 and 2-9 haveco-extensive axial apertures 3i through which they are journalled on atransparent cylindrical plug 42 which is carried by, and depends from,the fixed top plate til. The discs 22, 26, 21, 28 and 29 are rotatablymounted with their peripheries in arcuate recesses or grooves 4| in thespacers 36 (Fig. 4), and are thus held spaced from one another. Thetrack pointer 25 is journal'led on the transparent plug 42 (seeparticularly Fig. 3) carried by the disc 30 and extending inwardlytherefrom coaxially of the several discs. A retainer ring 45 on the plug42 prevents axial removal of the track pointer 25 therefrom. The tracklink 23 is preferably held slidalble on the wind direction disc 22 bythe four-bar linkage 24 which is interposed between said tra-ck link 23and the track pointer 25.

Referring now particularly to Fig. 6, the wind velocity disc 2| isinscribed with a concentric scale 50, preferably 270 in extent andgraduated to represent wind velocities in miles per hour, thegraduations being preferably uniformly spaced. The disc 2| is funtherprovided with a spiral cam slot whose maximum radius is radiallyopposite the zero point of the scale Eli and whose minimum radius isradially opposite the maximum point on said scale which is herein shownas representing 50 miles per hour.

The .wind direction disc 22 has inscribed thereon a radial index line52, and is formed with a cut-out guideway 53 which is disposed radiallyor diametrically of the disc 22 and whose central line is in alignmentwith the index line 52. Movable in the guideway 53, for movementdiametrically of the disc 22, is a slide 54 which carries the previouslymentioned floating pivot l9. The side edges of the slide 5e may slidablyengage d the parallel edges or the guideway '53, or, preferably, saidslide is provided with disc-like rollers 55 (Fig. 2) which ride ingrooves 5'5 in said guideway edges. The slide El i carries a downwardlyprojecting pin or follower M which is received by the spiral cam slotiii in the Wind velocity disc 2!, whereby the position of the slide 54in its guideway 53 is determined by the relative angular position of thediscs 24 and 22.

As best shown in Fig. 6, the heading disc 25 is inscribed with a radialindex line 6%, and formed with a radial slot iii the longitudinal axisof which is coextensive with the radial index line 6d.

The air speed disc 2l-is inscribed with a concentric scale 65, graduatedto represent altitudes in thousands of feet. Said disc 2? is alsoprovided with a spiral cam slot at which receives the previouslymentioned pivot or stud l8 (Fig. 1) that extends also through the radialslot 6! (Fig. 6) in the heading disc 26, whereby the radial position ofthe pivot 58 in said slot ti is determined by the relative angularposition of the discs 26 and 2'5.

Again referring to Figs. 2 and 6, the air speed correction disc 28 isinscribed about a portion of its margin with a concentric scale 68,graduated to represent temperatures, preferably in degrees Fahrenheit,and about the remainder of its margin with a concentric scale 62,graduated to represent indicator air speeds in miles per hour. Thetemperature scale til on the air speed correction disc 28 is adapted tocooperate with the altitude scale 65 on the air speed disc 2! to applyair speed correction for altitude and temperature.

The magnetic compass disc 29 is inscribed with a concentric scale lll,graduated in degrees and indicating azimuth compass bearings. The disc29 is further inscribed with a radial arrow or reference line i l.

The top or true compass point disc 3! is inscribed with a concentricscale 15, graduated in degrees and reading in azimuth, and preferablyalso with a second concentric scale it, marked with the usual points ofthe compass. The top disc 36 is preferably further inscribed with anarcuate scale l'l, graduated in degrees and indicating magneticVariations east and west.

The index lines 52 and [ill on the discs 22 and 26, respectively, aswell as the track pointer 25, are adapted to cooperate with either scale10 or 15 on the magnetic compass disc 28 and the top disc 39,respectively (see particularly Fig. 2). The index line 52 on the winddirection disc 22 is further adapted to cooperate with the scale 7 6 onthe top disc lid; The arrow ll on the magnetic compass disc 22 isadapted to cooperate with the compass variation scale H on the top disc38.

Referring now to Figs. 2 and 6, the track link 23 is formed with acentrally disposed, longitudinal slot 89 along the side or sides ofwhich is inscribed the earlier mentioned ground speed scale I'l,uniformly graduated to represent ground speeds in miles per hour. Thelink 23 carries at the zero point of the scale l! the previouslymentioned pivot or stud it, while the slot slidably receives thepreviously mentioned pivot or stud I 9 on the slide 54 in the winddirection disc 22.

The scales till, 65, 68 and E59, representing wind velocities,altitudes, temperatures and air speeds, respectively, being circularlyarranged, permit a wider range, more open spacing and larger marking, oftheir graduations than would be possible with rectilinear scales. Theseveral circular scales 10, 15, 88, 69, 85, 50, 18 and 11, whileconcentrically disposed, are located at different radial distances fromthe common axis a: of the instrument so that, in all positions ofadjustment, all are clearly visible and unobscured by any of the others,and, therefore, can be easily read. The ground speed scale 11 on thetrack link 23 cooperates with the pivot I9, as mentioned, and in allpossible positions of adjustment, the position of the pivot I9 and ofthe portion of the scale I1 adjacent thereto is within, or removed from,all of the other scales, whereby said ground speed scale can be readwithout any interference from the other scales.

The instrument described so far, with the exception of the transparentplug 42 and the track pointer 25, is in most respects like theinstrument shown and described in my mentioned prior Patent No.2,357,131. The track pointer 25, which is rotatable about the plug 42,is drivingly connected with the track link 23 by the four-bar linkage24, which is similar in function to that shown and described in mycopending application Serial No. 495,089, filed July 1'1, 1943, nowPatent No. 2,376,006, granted May 15, 1945. However, the linkage 24 ofthe present application is so arranged and connected with the track link23 and track pointer 25 that no part of the linkage or pointerencroaches upon the scale 11 in any operative position of the track link23. Thus the present arrangement distinguishes from that shown in mysaid prior Patent No. 2,376,008 in that a clear view of the scale 11unencumbered by the linkage 24 and track pointer 25 is provided fromabove. The linkage 24 is so constructed and arranged that the trackpointer 25 will always maintain the same relative angular disposition.to and preferably extend parallel to the track link 23 in any positionof the latter. The linkage 24 comprises two pairs of paral-' lel links85 and 88, of which the links 85 are pivotally connected at 81 and 88with the track link 23 and a floating spacer 89, respectively (Figs. 2and 6). One of the other links 88, to wit 86', is turnable on the plug42 (Fig. 3) and pivotally connected at 80 with the floating spacer 89,while the remaining link 86 is pivotally connected at BI and 92 with thefloating spacer 89 and the track pointer 25, respectively. The variouselements of the four-bar linkage 24 are so located in spaced parallelplanes (Figs. 2 and 3) that the center line or slot 80 of the track link23 may relatively shift to either side of the track pointer 25 which,however, maintains the same relative angular disposition and preferablyremains parallel to it, according to the circumferential and radialadjustment of the indicator l9 about the axis and sweep through amaximum range the limits of Which are reached only when the links ofeither pair 85 or 88 engage each other.

The use of the instrument may be explained in connection with thefollowing illustrative example, reference being had particularly to Fig.2. Assume that a flight is to be undertaken to an objective whose truebearing is azimuth 75, that the compass variation for the locality is 20east, that the indicated air speed of the plane is 150 miles per hour,that the pilot is flying at an altitude of 5000 feet, that thetemperature is +80 F., and that the wind is blowing 40 miles per hourfrom the northwest. The instrument may then be set as follows: Themagnetic compass disc 29 is turned until the arrow 1| thereon points tothe 20 east variation mark of the scale 11 on the non-rotatable top ortrue compass point disc 30 and the zero mark of the azimuth scale 10 onsaid magnetic compass disc 29 aligns with the 20 mark of the azimuthscale 15 on said top disc 30.

Next, the air speed correction disc 28 may be set relative to the airspeed disc 21 to undertake the correction in the indicated air speed ofthe plane in accordance with the flight altitude and air temperature. Tothis end, the air speed correction disc 28 may be turned relative to theair speed disc 21 until the F. mark of the temperature scale 88 on theformer disc aligns with the 5000 ft. mark of the pressure altitude scaleon the latter disc.

Next, the instrument may be set in accordance with the indicated airspeed of the plane miles per hour). To this end, the air speed disc 21and relatively adjusted air speed correction disc 28 are turned inunison relative to the heading disc 28 until the 150 mile per hour markof the speed scale '89 on the disc 28 aligns With the index line 80 onthe disc 28. The indicated air speed scale 89 on the disc 28, the spiralcam slot 86 in the disc 21 and the index line 88 and radial slot 8| inthe disc 28, are so coordinated that, if the discs 21 and 28 wereadjusted for sea level or zero altitude and +60 F. (zero mark ofpressure altitude scale 85 aligned with +80 F. mark of temperature scale88) for reasons hereinafter explained, and the instrument set oradjusted for an indicated air speed of 150 miles per hour, the fixedpivot [8 on the track link 28 would be shifted in the radial slot 8|into a position in which its distance from the fixed axis a: of theinstrument represents, in the calibration of the ground speed scale 11on the track link 23, the indicated air speed (150 miles per hour).Hence, by setting the instrument for zero altitude and +60 the true airspeed as represented by the distance of the pivot 18 from the axis a: isthe same as the indicated air speed for which the instrument is set, andno correction of the true air speed due to altitude and temperaturetakes place. The reason for this lies in the standard practice to givethe indicated air speed of a plane at +60 F., and at sea level or zeroaltitude, and the scales 85, 88 and 89 are so arranged and coordinatedthat the true air speed is the same as the indicated air speed when theinstrument is set for the latter speed and the standard temperature +60F. and zero altitude. For any other altitude and temperature setting ofthe instrument, the indicated air speed scale 88 is so adjusted relativeto the piral cam slot 88 that, on. setting the instrument for a certainindicated air speed, the corresponding altitude and temperaturecorrection is included in the true air speed as represented by thedistance of the pivot l8 from the fixed axis as of the instrument. Theexact arrangement of the temperature and pressure altitude scales 88,85, and their cooperation with the indicated air speed scale 89, isfully shown and described in my beforementioned prior Patent No.2,357,131, and requires no further explanation herein.

Next, the instrument may be set in accordance with the direction of thewind (northwest). To this end, the wind direction disc 22 is turneduntil the index line 52 thereon aligns with the NW mark of the scale 18on the top disc 30, thereby also bringing the floating pivot 19 on theslide 54 diametrically opposite said NW mark.

The instrument may next be set in accordance with the velocity of thewind (40 miles per hour). To this end, the wind velocity disc 2| isturned relative to the set wind direction disc 22 until the index line52 on the latter disc aligns with the 40 miles per hour mark of thescale 53 on the former disc, whereby the slide at is shifted in the disc22 until the pivot It thereon assumes a position in which its distancefrom the fixed axis a: of the instrument represents, in the calibrationof the ground speed scale H on the track link 23, the wind velocity (40miles per hour). An imaginary straight line drawn from the pivot 59 tothe fixed axis x of the instrument (Fig. 2) constitutes a wind directionand velocity vector such as the vector 1) in Fig. 1.

The instrument is then finally set in accordance with the true bearingof the objective (azimuth 75 To this end, the heading disc at and theair speed disc 21 with the relatively adjusted air speed correction disc28, are turned in unison relative to the set wind velocity and directiondiscs 2|, 22 until the track pointer 25 align with the '75 mark of theazimuth scale 15 on the top disc 3!] whereby said track pointer 25 alsoindicates on the azimuth scale 10 of the set disc 29 (Fig. 2) themagnetic bearing of the objective (azimuth 55). The track link 23 is, ofcourse, moved with the track pointer, as explained, and remains parallelwith the latter. An imaginary line then drawn from the pivot it to thefixed axis a: (Fig. 2) constitutes a true air speed and heading vectorsuch as the vector at in Fig. 1.

The instrument being now set, the magnetic heading is indicated by theindex line it of the heading disc 26 on the azimuth scale it of the disc29 (and the true heading on the azimuth scale l5 f the top plate 39),while the ground speed is indicated on the scale ll of the track link 23opposite the pivot 19. The adjustments above described, and illustratedin Fig. 2, show that in order to fly a track whose true bearing isazimuth 75 under the conditions above stated, the pilots magneticheading should be azimuth 44, and that the ground speed of the plane isabout 183 miles per hour.

As previously mentioned, all the scales of the instrument, except theground speed scale 0n the track link 23, are arranged circularly and atdifferent radial distances from the axis x of the instrument, whereforethey permit a wider range, more open spacing and larger marking of theirgraduations than would be possible with rectilinear scales. The openspacin and large marking of the graduations of these circular scalesrenders them legible to the user of the instrument despite thecumulative glare resulting from light reflection from the surfaces ofthe discs and any lack of complete or clear transparency of the latter.However, the graduations of the rectilinear ground speed scale ll are ofnecessity relatively closely spaced in order that said scale may havethe wide speed range dictated by the adjustability of the instrument tothe wide variation in the indicated air speed of modern aircraft and toa wide range of the wind velocity. It is for the purpose of preventingthe lack of complete transparency of, and glare from, the discs andother parts overlying the track link 23 'from obscuring and interferingwith the clear reading of the ground speed scale ll, that the plug 552,which is a unitary piece of clearly transparent material, has beenmounted in the instrument as the sole intervening element between saidscale ii and the eyes of the user of the instrument. The diameter of theplug 42 and of the central apertures of the discs through which itpasses, is such that the portion of the ground speed scale li adjacentthe pivot l9 lies, for any setting of the instrument, within thecircular confines of said plug and apertures, so that the ground speedcan always be distinctly read through the plug 42. Furthermore, thetrack link 23 is made so wide that neither side edge thereof appearsbehind the plug &2 in any setting of the instrument, so that the pivotI9 and the portion of the scale I! adjacent thereto are the onlyelements that appear to the eye behind the plug 62 against the otherwiseuniform background of the track link 23.

I claim:

1. A navigation instrument, comprising a straight graduated speed scalehaving an integral pivot at the zero point of the graduation, atransparent compass dial at one side of, and parallel to, said scale andhaving a central transparent cylindrical plug extending toward saidscale, transparent elements journalled on said plug and relativelyturnable for moving said pivot Parallel to said dial into any positionwithin certain limits, a radial pointer journalled on said plug and c0-operating with said dial, a linkage so drivingly connectin said scaleand pointer that they are parallel in any position, and so arranged thatsaid linkage remains outside the confines of said plug in any positionof said scale, a second pivot slidable on said scale, and means at theother side of said scale for movingsaid second pivot parallel to saiddial into any position within certain limits, the diameter of said plugbeing such that said second pivot and the scale graduations nearestthereto are visible therethrough in any position of said scale.

A navigation instrument, comprising a straight graduated speed scalehaving an integral pivot at the zero point of the graduation, atransparent compass dial at one side of, and parallel to, said scale andhaving a central transparent cylindrical plug extending toward saidscale, transparent discs journalled on said plug, one of said discshaving a radial slot slidably receiving said pivot and the other dischaving a cam for shifting said pivot in said slot on relative rotationbetween said discs, a radial pointer journalled on said plug andcooperatin with said dial, a linkage so drivingly connecting said scaleand pointer that they are parallel in any position, and so arranged thatsaid linkage remains outside the circular confines of said plug in anyposition of said scale, a second pivot slidable on said scale, and meansat the other side of said scale for moving said second pivot parallel tosaid dial into any position within certain limits, the diameter of saidplug being such that said second pivot and the scale graduations nearestthereto are visible therethrough in any position of said scale.

3. A navigation instrument comprising a straight graduated speed scalehaving an integral pivot at the zero point of the graduation, atransparent compass dial and cooperating coaxial relatively turnabletransparent elements at one side of, and parallel to, said scale andhaving apertures therein, at least one of said turnable elements beingarranged for moving said pivot parallel to said dial into any positionwithin certain limits, a radial pointer cooperating with said dial andturnable coaxially of it, a linkage so drivingly connecting said scaleand pointer that they may move cooperatively to any relative position inplanes parallel to said dial within certain limits, in such manner thatthey always maintain the same relative angular disposition in any suchrelative position, and so arranged that said linkage remains outside thelimits of visibility through said aper- 9 10 tures in any position ofsaid scale, a second pivot Y slidable on said scale, and means at theother side REFERENCES CITED of said scale for moving said second pivotparallel The following references are of record in the to said dial intoany position within certain limits, file of this p t t! the areas ofsaid apertures being such that said UNITED STATES PATENTS second pivotand the scale graduations nearest thereto are visible therethrough inany position of Number Name Date said scale, and support membersmaintainin said 7 Bennett Feb. 7, 1933 scale, burnable elements andpointer in cooperatu 2,341,924 Kruck Feb. 15, 1944 mg operativeinterrelation. 10 6,00 Putnam May 15, 1945 JOHN P. PUTNAM.

